1. Field of the Invention
The present invention relates to systems and methods useful for stabilizing platforms and vessels having platforms, which vessels include self-elevating vessels such as liftboats and stationary drilling platforms. More particularly, the present invention relates to systems and methods that include braces adapted to be coupled to one or more legs of a vessel, such as a liftboat. The present invention also relates to methods and systems useful in stabilizing the platforms on such vessels. The use of the present systems with traditional vessels creates the present vessels.
2. Description of Related Art
Vessels having platforms that may be raised or lowered along three or more legs have been used in the marine industry for many years as mobile service centers for offshore oil and gas production platforms. These vessels are known by different names depending on, for example, the size of the platform, the size of the cargo supported by the platform, and/or the length of the legs. Some such designations include “liftboats” and “jack-up boats.” In addition, stationary vessels known as “jack-up platforms” include the same type of platform and leg arrangement that liftboats and jack-up boats have.
With the exception of jack-up platforms, these vessels are generally self-propelled, meaning that they do not require a tug or a barge to advance them through a body of water. These vessels are also self-elevating, meaning that once the vessel has reached its designation, the platform—which is referred to by some as a barge—may be raised or lowered along the length of the legs using, for example, a hydraulic driving, or jacking, mechanism that may include a combination of racks and pinions. In operation, these vessels may be propelled toward their destination under their own power, or by the power of others, such as tugs or barges. Once the vessel is in place, the legs, which during transit were raised sufficiently off the ocean floor to avoid getting caught on anything sticking up from the ocean floor, are driven downwardly until they have firmly contacted the floor. Next, and using the same driving mechanisms that caused the legs to descend, the platform is raised along the legs to a desired height, and work may begin. These legs may be made of tubular steel, the diameters of which generally increase with increases in length (i.e., longer legs are generally greater in diameter than shorter legs). The legs may also be made of truss-type structures. A figure depicting a traditional liftboat is illustrated in FIG. 1 (liftboat peripherals, such as deck cargo and the like, are not depicted).
In addition to their usefulness as the mobile service stations described above, these vessels are useful for practically any type of work that requires a portable base in a marine environment. Cranes, cameras, crews, and cargoes of any kind may be transported, loaded, and unloaded off of the stable platforms these vessels provide. Their uses are virtually unlimited.
The forces to which the legs of these vessels are normally subject are numerous and potentially damaging. For example, the vertical loads that are applied to the legs by virtue of the weight of the platform and the various deck cargoes can cause the legs to buckle. Furthermore, the legs may be bent by the horizontal forces that result from the wind and waves. Additionally, when floating in transit, the raised legs can make the vessel top-heavy and, as a result, capsize. If the weather is inclement when the vessel is floating, the legs may also be damaged by whipping due to rolling or pitching.
As mentioned above, and in an effort to address one or more of these problems, some legs are made of truss-type structures. However, design and proportional constraints have limited the dimensions of the triangular sections of these structures, rendering them ineffective for adequately addressing these problems. Furthermore, increasing the diameters of tubular legs has not proven to be an adequate way of addressing the foregoing problems due to the same types of design and proportional constraints.
Traditional anchors have also been utilized in an attempt to address the problems associated with the forces to which the legs of traditional vessels are normally subject. In this regard, it is known in the art to drop multiple anchors connected to the platform of traditional vessels at predetermined locations with a body of water in an attempt to stabilize the position of the vessel. This may be done by arranging multiple anchors (usually 3, 4, or more) connected to chains or the like in a manner that allows the vessel to come symmetrically to rest between them. However, such use of anchors suffers from various problems, including, for example, the tendency of the anchor to shift in surroundings defined by mud, or other soft or loose material.
The problems pointed out with the foregoing leg designs are not intended to be exhaustive but rather are among many that tend to impair the effectiveness of previously known legs. Other noteworthy problems may also exist; however, those presented above should be sufficient to demonstrate that previous techniques appearing in the art have not been altogether satisfactory, particularly in achieving a vessel with a stable set of legs.